The present invention relates to a semiconductor wafer cleaving method and apparatus by which semiconductor wafers are cleaved along scribing marks.
Since priorly, various types of semiconductor chips have been obtained by cutting off a plurality of element areas formed and arrayed on a semiconductor wafer at boundary positions. Recently, the cutting of semiconductor wafers is carried out by, for example, cleaving the wafers along scribing marks with the scribing marks provided at boundary positions of the element formed areas at the end edge on the surface of the semiconductor wafers.
FIG. 11 and FIG. 12 show a conventionally general method for cleaving semiconductor wafers. The cleaving method is called a xe2x80x9cthree-point bending method.xe2x80x9d First, a plurality of scribing marks 2 are arrayed and formed at the end edge on the surface of a semiconductor wafer 1 (These scribing marks 2 are provided at the boundary positions of the element formed areas on a semiconductor wafer 1). Next, a pair of fulcrum members 4a and 4b are disposed in parallel to the scribing marks 2 with each of the scribing marks 2 placed therebetween on the surface 3 where the scribing marks are formed. Also, on the rear side 5 opposite the scribing mark formed surface, a fulcrum member 6 is disposed so as to become parallel to each of the scribing marks 2, at the position opposed to the above scribing marks 2. After that, a tensile force is given to the scribing marks 2 by causing fulcrum forces P2, P1, and F1 to operate thereon from these fulcrum members 4a, 4b and 6, whereby the semiconductor wafer 1 is cleaved at the plane ZOY from the position of the scribing marks 2.
The relationship between a shearing force and a bending moment in carrying out a cleaving by the xe2x80x9cthree-point bending methodxe2x80x9d is expressed as shown in FIG. 13. As shown in FIG. 13, the positive or negative polarity of the shearing force is reversed at the lower fulcrum member 6 used as the boundary. In fact, the operating point of a fulcrum force F1 acting from the fulcrum member 6 on the semiconductor wafer 1 has a definite width although being slight. Therefore, the shearing stress does not become zero in the entirety of the operating area of the fulcrum force F1. As shown in FIG. 12, a portion of a minute cubic volume dva of one-sided half of the scribing mark is taken for instance, wherein a shearing stress xcfx84 parallel to the plane ZOY to be cleaved, and a bending tensile stress "sgr"ax perpendicular to the plane ZOY to be cleaved are produced.
If the shearing stress and bending tensile force are expressed in terms of Mohr""s stress circle, they will become as shown in FIG. 14. That is, the direction of action of the ruling maximum main stress "sgr"a1 of cleavage produced on the cleavage plane of the scribing mark is not a direction "sgr"ax perpendicular to the vertical cleavage plane (plane ZOY) ideal to the semiconductor wafer 1, but has an angle xcex11 from the direction "sgr"ax, (which can be easily calculated by Mohr""s stress circle). Therefore, as in the cleavage plane of a cleavage state illustrated in FIG. 15, an oblique cleaved portion 7a is produced at the portion at the lower side of the scribing mark 2 on the cleavage plane 7 of the semiconductor wafer 1, whereby such a problem arises, by which an expected cleavage plane could not reliably be obtained.
In addition, as shown in FIG. 16, when actually carrying out a cleaving work, the fulcrum member 6 does not become parallel to the scribing marks 2, whereby a possibility exists, that the fulcrum member 6 is disposed so as to cross the extension line of the scribing marks 2. In such cases, a problem arises, by which a cleavage plane 7 bent as shown in FIG. 17 would be produced.
The present invention was developed in order to solve the above shortcomings and problems, and it is therefore an object of the invention to make the shearing stress zero in the vicinity of the scribing marks, and to make the direction of the maximum main stress produced in the scribing mark perpendicular to the ideal vertical cleavage direction. That is, the invention is to provide a semiconductor wafer cleaving method and apparatus which enables an ideal mirror-finished cleavage plane by operating only the bending tensile stress onto scribing marks.
The invention is constructed as described below. That is, a first aspect of a semiconductor wafer cleaving method according to the invention is constructed so that the lower side of a semiconductor wafer, which has a scribing mark inscribed on the surface, is supported by fulcrum members in parallel to the above scribing mark at least two or more positions between which the scribing mark is placed, and similarly, the upper side of the semiconductor wafer is supported by fulcrum members in parallel to the above scribing mark in at least two or more positions, between which the scribing mark is placed, different from the positions where the scribing mark is supported so as to be placed at the innermost side on the lower side, a fulcrum force, which makes zero the shearing force of a semiconductor wafer between the fulcrum members supporting the innermost side with the scribing mark placed therebetween, is given from the respective fulcrum members at both upper side and lower side to the semiconductor wafer to cause pure bending tensile stress to operate onto the scribing mark, and the semiconductor wafer is cleaved at the scribing mark.
Further, a second aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first aspect of the semiconductor wafer cleaving method, the fulcrum members at both upper side and lower side of the semiconductor wafer are placed left-right symmetrically, centering around a scribing mark, and a left-right symmetrical pair of fulcrum members which support at the innermost side the plane where the scribing mark is formed, are disposed outside the corresponding left-right symmetrical pair of fulcrum members which support at the innermost side the opposite back side.
Further, a third aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first or second aspect of the semiconductor wafer cleaving method, one side of the upper side fulcrum members and the lower side fulcrum members of the semiconductor wafer are caused to move in a direction of applying a fulcrum force when applying a fulcrum force from the respective fulcrum members to the semiconductor wafer, the moving side fulcrum members are supported via a slide mechanism which self-adjusts the hypothetical plane connecting the fulcrum tip ends of the above moving side fulcrum members in parallel to the plane in which a fulcrum force of the semiconductor wafer is applied, and the slide mechanism causes the moving side fulcrum members while maintaining the parallel of the above hypothetical plane of the moving side fulcrum members with respect to the plane in which a fulcrum force of the semiconductor wafer is applied, whereby a fulcrum force is applied to the semiconductor wafer.
Also, a fourth aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first, second or third construction of the semiconductor wafer cleaving method, a fulcrum force of a fixed load is applied from the upper side fulcrum members and the lower side fulcrum members of a semiconductor wafer.
Moreover, a fifth aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first, second or third construction of the semiconductor wafer cleaving method, a fulcrum force applied from the above fulcrum members to a semiconductor wafer is a distributional load, the force of which is increased in the direction a crack generated along the scribing mark develops.
Further, a sixth aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in the construction of any one of the first through the fifth aspects of the semiconductor wafer cleaving method, a semiconductor wafer is cleaved with a damper member secured between the upper and lower respective fulcrum members on the upper side and lower side of the semiconductor wafer.
Moreover, a first aspect of a semiconductor wafer cleaving apparatus according to the invention comprises a wafer setting plane for placing and setting a semiconductor wafer which has scribing marks inscribed on the surface; a moving stage means which is capable of moving the semiconductor wafer set on the wafer setting plane in the X and Y directions of two planar axes, orthogonal to each other and a rotation direction around a Z axis perpendicular to the plane XY; lower side fulcrum members for supporting the lower side of the semiconductor wafer placed on the above wafer setting plane in parallel to the scribing mark in at least two or more positions in a state where the scribing mark is placed therebetween, upper side fulcrum members for supporting the upper side of the semiconductor wafer set on the above wafer setting plane in parallel to the above scribing mark in at least two or more positions different from a position to support the above scribing mark at the innermost side at the above lower side in a state where the scribing mark is placed therebetween; a dynamic load applying means for applying a moving load for giving a fulcrum force from at least one of both the above upper side and lower side fulcrum members to the semiconductor wafer; and an observing means provided with a camera for observing a supporting situation of the semiconductor wafer supported by both the above upper side and lower side fulcrum members; wherein a fulcrum force which makes zero a shearing force of the semiconductor wafer between the fulcrum members to support the innermost side with the scribing mark placed therebetween is applied from the respective fulcrum members at both the upper side and lower side to the semiconductor wafer, and pure bending tensile stress is caused to operate onto a scribing mark, whereby the above semiconductor wafer is cleaved on the basis of the above scribing mark.
Further, a second aspect of the semiconductor wafer cleaving apparatus according to the invention is characterized in that, in addition to the first construction of the semiconductor wafer cleaving apparatus, the respective fulcrum members in which a moving load is applied from the dynamic load applying means are connected to the above dynamic load applying means via a slide mechanism which self-adjusts the hypothetical plane, which connects the fulcrum tip ends of the semiconductor wafer of the above respective fulcrum members, in parallel to the plane where a fulcrum force of the semiconductor wafer is applied.
In the invention, fulcrum members are disposed at two or more positions between which a scribing mark is placed, on the scribing mark formed plane of a semiconductor wafer. Further, fulcrum members are also disposed at two or more positions, between which the scribing mark is placed, on the side opposite the scribing mark formed plane as in the above. Since a fulcrum force is applied from the respective fulcrum members, a shearing stress becomes zero at the area of the semiconductor wafer between the fulcrum members having the above scribing mark placed at the innermost side therebetween. Therefore, the maximum main stress of a bending tensile force is caused to act onto the scribing mark in a direction perpendicular to the ideal vertical cleaving plane, whereby the semiconductor wafer is cleaved along the ideal vertical cleaving plane at the position of the scribing mark. Therefore, the cleaved plane can be prevented from becoming oblique or being bent at both ends or at one side of the scribing mark, wherein it is possible to obtain an ideal mirror-finished vertical cleaved plane.
The invention brings the following effects. That is, the lower side of a semiconductor wafer, on which a scribing mark is inscribed is supported by fulcrum members at two or more positions between which the scribing mark is placed, and as in the above, the upper side of the semiconductor wafer is supported by fulcrum members at two or more positions between which the above scribing mark is placed, whereby a fulcrum force is applied from the fulcrum members so that the shearing force becomes zero at the areas of the semiconductor wafer between the fulcrum members which place the scribing mark at the innermost side therebetween, thereby causing the semiconductor wafer to be cleaved. The invention is constructed so that the semiconductor wafer is thus cleaved. Therefore, the semiconductor wafer can be cleaved by causing only pure tensile stress of the maximum main stress to operate in a direction orthogonal to the perpendicular plane of the semiconductor wafer along the scribing mark.
Therefore, it is possible to obtain an ideal mirror-finished perpendicular cleaved plane which is straight along the scribing mark, wherein the cleavage quality can be remarkably improved. In addition, since the shearing stress can be made zero in the entire range between the fulcrum members at the innermost side, work for aligning the scribing mark to the range where the shearing stress is zero can be facilitated, wherein the efficiency of the cleaving work can be further improved.
Moreover, fulcrum members at both the upper side and lower side, which support a semiconductor wafer, are left-right symmetrically disposed, centering around the scribing mark, and a load is applied from one of either the upper side or the lower side or both to a semiconductor wafer on load applying planes parallel to both the upper side and lower side of the semiconductor wafer. Since the load is thus applied, the fulcrum force operating from the respective fulcrum members onto the semiconductor wafer is made equal, wherein the shearing force between the fulcrum members which support the innermost of the wafer necessarily becomes zero. Accordingly, it becomes very easy to adjust the shearing stress between the fulcrum members, between which the scribing mark is placed, to zero.
Further, since both the upper side and lower side of the semiconductor wafer are covered up with a damper means when cleaving the corresponding semiconductor wafer, the semiconductor wafer can be prevented from being impaired and damaged. In addition, it is possible to prevent the cleaved semiconductor wafers from being scattered.
In addition, since it is constructed so that the fulcrum members are connected to a dynamic load applying means via a slide mechanism, the hypothetical plane connecting the operating points of fulcrum forces of the respective fulcrum members is self-adjusted to become parallel to the operating plane of the fulcrum forces on the semiconductor wafer, wherein load is applied onto the fulcrum members. Therefore, such an effect can be obtained, by which load uniformly distributed to the respective fulcrum members can be applied from the dynamic load applying means.
Further, since it is constructed so that a fulcrum force in a distributional load pattern in which the force is gradually increased in line with the advancement of a crack is applied to the semiconductor wafer, the crack advancement speed can be accelerated at the scribing mark formed plane side. Thereby, when cleaving a semiconductor wafer in which a complex layer such as metallic plating, etc., is formed on the scribing mark formed plane, the cleaved plane can be prevented from becoming defective, and good quality and stabilized cleaved planes can be obtained.